Proteoglycans have further been identified and characterized in cells participating in allergic reactions. Human eosinophils have been shown to contain a highly charged proteoglycan chondroitin 4-sulfate. The proteoglycan heparins of the rat mast cell have been examined to determine sub-group characteristics which have functional implications. Preparations are underway to develop an animal model of food hypersensitivity. Preliminary experiments are designed to correlate gastrointestinal mast cell number with histamine content and further, to attempt to release this histamine both in vivo and in vitro. Development of protocols to study human mast cells and their pathophysiologic function in mastocytosis and cold urticaria.